Propeller coupling

ABSTRACT

A hydraulic actuated propeller coupling for use in a helicopter type aircraft to selectively couple or uncouple a propeller to the output of a gas turbine engine normally used to drive a helicopter rotor.

United States Patent Wagner 1451 July '25, 1972 s4] PROPELLER COUPLING[56] References Cited [7 21 Inventor: Douglas A. Wagner, Indianapolis,Ind. UNITED STATES PATENTS [73] Assignee: Gener l Motors Corporation, Deroit, 3,063,529 11/1962 Cook ..192/53 B Mich. 2,217,883 10/1940Anderson. 416/169 X 776,404 11/1904 Keyser 192/53 B [22] Filed: Nov. 30,1970 2,698,147 12/1954 Hovgard 416/170 X 3,300,004 1/ 1967 Peterson..192/53 F X [21] Appl. No.: 93,605

Primary ExaminerAllan D. Herrmann 52 0.5. CI ..192/4a.7, 74/665 F,192/53 B, momeyqm ca'pemer and 192/114, 244/17.21,4l6/l69,416/170 [57]ABSTRACT [51] II."- C] ..Fl6d 23/04 A hydraulic actuated propeller pu gfor use in a helicopter [58] Field of Search ..l92/48.7, 53 F, 53 B;416/ 169, type i f to selectively couple or uncouple a propeuer to theoutput of a gas turbine engine normally used to drive a helicopterrotor.

5 Claims, 4 Drawing Figum Patented July 25, 1972 3,679,033

2 Sheets-Sheet 1 ENGXNE m 71 V/ X67 I; \la

INVENTOR.

Patented July 25, 1972 3,679,033

2 Sheets-Sheet 2 INVENTOR.

gag/as AVWzgner AT TORN EY PROPELLER COUPLING This invention relates toa propeller coupling and, in particular, to a propeller couplingarrangement whereby a propeller can be selectively driven by an enginenormally driving a helicopter rotor, the propeller being driven when itis desired to obtain a forward speed greater than that obtainable by useof the helicopter rotor alone.

In conventional helicopter type aircraft, the forward speed of suchaircraft is limited because the helicopter rotor is used both to providelift for the aircraft and to effect forward progress of the aircraft.However, there are times when it would be obviously advantageous tooperate such a helicopter type aircraft at forward speeds greater thanthat which could be achieved by the helicopter rotor itself.

-Accordingly, it is the principal object of this invention to provide apropeller coupling arrangement for use on a helicopter type aircraft toselectively drive a propeller when desired while still permittinghelicopter type mode of operation only, when desired.

Another object of this invention is to provide a propeller couplingarrangement which is hydraulically actuated to selectively couple apropeller to the output of a gas turbine engine.

Still another object of this invention is to provide a couplingarrangement between an input shaft and an output shaft in which a smalltorque force is applied through a clutch to synchronize the speeds ofthese shafts before effecting a positive drive interconnection betweenthese shafts.

These and other objects of the invention are attained by means of apropeller coupling arrangement for use in a helicopter type aircraft toselectively effect coupling and uncoupling of a propeller shaft to theoutput of a gas turbine engine. The gas turbine engine normally drives ahelicopter rotor through a drive gear train, which also includes a maindrive gear and shaft which is selectively coupled to a sliding splineshaft to drive the propeller shaft through a conventional planetary geardrive train. In this arrangement, the propeller is windmilled to bringthe propeller shaft to near synchronous speed with respect to the outputof the gas turbine engine, at which time, a disc clutch is brought intooperation to efiectively complete synchronization and then a synchronousclutch is engaged to effect complete synchronization after which thespline shaft is moved into engagement with the main drive gear wherebythe propeller is then driven by the gas turbine engine. These clutchesare hydraulically controlled to effect coupling and uncoupling of thepropeller shaft to the output of the gas turbine engine.

For a better understanding of the invention, as well as other objectsand further features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic side view of the engine power plant and drive geararrangement for a helicopter type aircraft for driving a main helicopterrotor, tail rotor and a propeller;

FIG. 2 is a sectional view of a portion of the gear case of FIG. 1showing the propeller coupling arrangement of the sub ject invention,with parts in the propeller engaged position;

FIG. 3 is a sectional view of a lock mechanism for the propellercoupling arrangement of the invention; and,

FIG. 4 is a sectional view similar to FIG. 3 showing the parts in thepropeller disengaged position and the hydraulic system for effecting itsoperation.

Referring to FIG. 1, an engine 10, such as a gas turbine engine, isconnected through reduction gears in a gear casing 11 to drive ahelicopter rotor and a tail rotor, not shown, through an angled driveshaft 12 and, above a predetemiined forward speed of the aircraft todrive a propeller 13. The gas turbine engine drives the rear end of afirst or power input shaft 14 through any suitable coupling, notillustrated. The input shaft 14 is coupled in the conventional manner toa shaft 15 carrying the helicopter rotor drive gear 16 and the pinion 17of a propeller shaft input gear train. As shown, pinion 17 drives anannular main drive gear 21 on tubular drive shaft 18 suitably journaledfor rotation in gear casing 11. Drive shaft 18 is provided with a set ofinternal splines 22 engageable with the external splines 23 on anaxially moveable hollow intermediate or spline shaft 24 through thecoupling arrangement of the invention to be described.

Spline shaft 24 is provided with internal splines 25 engaging externalsplines 26 on a hollow driven shaft 27 to drive a sun gear 28 of aplanetary gear set including planetary gears 31 and ring gear 32. Theplanetary gears 31 are rotatably journaled on trunnions 33 extendingaxially outward from a planet carrier 34 secured to the hollow propellershaft 35 which is preferably integral with the hub of propeller I3. Thenonrotating ring gear 32 is fixed to a portion of a gear casing 11 whilethe sun gear 28 is formed integral with the hollow driven shaft 27telescoped over the propeller shafl 35.

Referring now to the subject matter of the invention, the splines 23 onthe sliding spline shaft 24 are selectively moved into and out ofpositive driven engagement with the splines 22 on the drive shaft 18 bymeans of a disc clutch, a synchronous clutch and clutch actuatingmechanism to be described whereby the sliding spline shaft 24 is firstrotatably driven through the disc clutch to a speed correspondingapproximately to the speed of rotation of the drive shaft 18 after whichthe synchronous clutch is used so that the actual coupling together ofthese shafis cannot be effected until the rotational speed of the splineshaft 24 is synchronized with the rotational speed of the drive 'shaft.The coupling and uncoupling of the propeller shaft with the gas turbineengine is initiated by the pilot of the aircraft, as desired, throughthe operation of a single control switch.

Specifically, as shown in greater detail in FIGS. 2 and 4, the driveshaft 18 is provided at one end with a set of external splines 36 whichengage a set of internal splines 37 on a torque input member in the formof a clutch drive ring 38 journaled for rotation with the drive shaft 18on the gear casing 11 by means of a fixed bearing 41 with the clutchring being positioned axially by engagement of the inner race of thebearing 41 between a shoulder provided on the clutch drive ring and aretainer ring 42 fixed by screw ring 43 threaded onto one end of theclutch drive ring. At its other end, clutch drive ring 38 is providedwith internal splines 44 drivingly engaged with torque input meansincluding a plurality of stacked friction plates 45, a clutch backupring 46 and a cone-faced friction drive ring 47 with the ring 46abutting against a shoulder 48 of the clutch drive ring 38.

Interposed between the friction plates 45 and between these frictionplates and the rings 46 and 47 are a second set of stacked frictionplates 51 of a torque output means in the form of engaged with theexternal splines 52 at one end of a torque output member in the form ofclutch driven ring 53 rotatably journaled with respect to the driveshaft 18 and axially positioned thereby by means of its radial flange 54being slideably positioned between a bearing ring 55 abutting against aradial shoulder on the drive shaft 18 and an L-shaped bearing ring 56held by retainer 57 and a nut ring 58 threaded to the end of the driveshaft 18. The clutch driven ring 53 has internal splines 57 of a lengthsufficient to be at all times engaged with the external splines 58 onthe spline shaft 24. The clutch driven ring 53 of this disc clutchstructure is used together with the windmilling effect of the propeller,to be described, merely to drive the spline shaft 24 up to a speedapproximately equal to the rotational speed of the drive shaft 18.

Positioned adjacent to the last described disc clutch elements, to theright as seen in FIGS. 2 and 4, is a cylinder 61 fixed to gear casing11, the cylinder 61 having a T-shaped internal flange 62 forming with aclutch actuating piston 63 and a spline actuator piston 64, a pair ofvariable sized chambers or piston cavities 65 and 66, respectively asseen in FIG. 4. The disc clutch actuating piston 63 is slideable in thecylinder 61 between the radial wall of flange 62 and a first set ofsplit ring retainers 67 secured in a suitable groove provided in theleft-hand end of a cylinder 61 with a wave washer 69 positionedtherebetween to normally bias the actuating piston 63 to the right asseen in this figure. Clutch actuating piston 63 is provided at one endwith annular bearing surface ring 63a for engagement with plain outboardface of friction ring 47. The piston 63 is thus axially shiftable andabuttable against the friction plates 45 and 51 to exert a clamp-uppressure on these friction plates to effect rotation of spline shaft 24through clutch driven ring 53, these elements being referred to as thedisc clutch as previously described.

In a similar manner, spline actuator piston 64 is slideable between theradial wall of flange 62 and a spring retainer ring 68 abutting againsta second set of split ring retainers 67 spaced axially from the firstset of split ring retainers, the spline actuator piston being normallybiased to the left, as seen in FIGS. 2 and 3, by a spring 71 encirclinga reduced portion of the spline actuator piston with one end of a springabutting against this piston and the other end abutting against thespring retainer ring 68.

Spline actuator piston 64 is provided with a radially inward extendingflange 64a by means of which it is secured to the spline shaft 24 tomove it into and out of engagement with the drive shaft 18. Radialflange 64a is positioned between a bearing ring 72 abutting against theexternal splines 73 on the spline shaft 24 and an L-shaped bearing ring74 held by retainer 75 and a nut ring 76 threaded to the end of thespline shaft 24 whereby as the spline actuator piston is moved axiallywithin cylinder 61, it will move the spline shaft 24 axially with it.

The splines 73 on the spline shaft 24 are helical in configu ration andare positioned to engage the internal helical splines 77 of a torqueoutput means in the form of a friction driven ring 78 having a conicalfriction surface at its free end adapted to engage the conical frictionsurface of friction drive ring 47. The friction driven ring 78 isnormally biased into frictional engagement, to the left as seen in FIGS.2 and 4, with the friction drive ring 47 by means of a coiled spring 79encircling the driven ring 78 with one end of the spring abuttingagainst a shoulder of the friction driven ring 78 and its other endabutting against the actuator piston 64. These elements cooperating withfriction ring 47 constitute the synchronous clutch previously referredto, the operation of which will be described in detail hereinafter.

Cylinder 61 is provided with through passages 83 and 84 and through ventpassage 85, as shown in FIGS. 2 and 4, with the passages 83 and 84positioned directly adjacent and on opposite sides of the radial wall offlange 62 for communication with chambers 65 and 66, respectively, whilevent passage 85 is positioned to be selectively closed by the outerperipheral body of spline actuator piston 64 or to be opened to serve asa vent, as the reduced portion of this piston 64 overlies this ventpassage.

Operation of the clutch actuator piston 63 and spline actuator piston64, in a manner to be described, is effected by hydraulic fluid suppliedby pump 86 from fluid sump 87 at a suitable operating pressure, theupper limit of which is controlled as by a pressure relief valve 88. Theflow of hydraulic fluid to and from the passages 83, 84 and 85 iscontrolled by a pilot actuated valve, such as a solenoid valve 91, aPitot pressure actuated valve 92 and a shuttle valve 93.

Solenoid valve 91 has a valve body 94 and a valve spool 95. The valvespool 95 is slideably disposed within a bore in the valve body tocontrol fluid flow from either port 96 or 97 to a port 98 and isnormally biased to a closing position with respect to port 96 by aspring 99.

Pitot pressure actuator valve 92 has a valve body 101 and a valve spool102. Valve body 101 has a central bore 103 and reduced bores 104a and10411 on opposite sides thereof in communication with ports 105 and 106,respectively. The valve spool 102 has three equal size lands a, b andequally spaced from each other and slideably received within the bore103, with the central land b being selectively moveable to place eitherport 107 or 108 in communication with the port 109. Spring 110 normallybiases the valve spool to the left, the position shown in FIG. 4, whilePitot pressure admitted through port 105 is used to move the valve spoolto the right against the biasing action of this spring.

The shuttle valve 93 has a valve body 111 and a valve spool 112. Valvebody 111 has a central bore 113 and reduced stepped bores 114a and 114bon opposite sides thereof. The valve spool 112 has three equal sizelands :1, e, and f slideably received within bore 113 with the centerland e being used to control the flow of fluid from a port 115 incommunication together with ports 116, 117, 118 and 119 with the bore113 in the valve body. The valve spool 112 is normally biased to theposition shown in FIG. 4 by springs 121 acting on opposite sides of thevalve spool 112.

As shown in FIG. 4, the discharge from the pump 86 is connected by aconduit 131 having an orifice 132 therein and by a conduit 133 to thebore 114b of the shuttle valve 93 and by conduit 134 to passage 85. Inaddition, conduit 131 is connected by a conduit 135 to port 97 of valve91, by a conduit 136 to the port 108 of valve 92 and, by conduit 137 toport 115 of valve 93.

The ports 116 and 117 of valve 93 are connected by conduits 141 and 142,respectively, to a conduit 143 which in turn is connected to a returnconduit 144 emptying into the sump 87. In a similar manner, the port 107of valve 92 is connected by a conduit 145 to the conduit 144 for returnof hydraulic fluid to the sump. Passage 83 is connected by conduits 146and 147 to the ports 118 and 119, respectively, of the valve 93, whilepassage 84 is connected by a conduit 148, having an orifice 149 therein,to the bore 114a of valve 93 and by a conduit 151 extending therefrom tothe port 98 in valve 91. Port 96 of this valve is then connected by aconduit 152 to the port 109 of valve 92. In addition, the port 106 ofvalve 92 is suitably connected by a conduit 153 to the sump 87 for thereturn of any hydraulic fluid which may leak across the land c of thespool valve 102.

Since hydraulic fluid pressure from pump 86 is normally not availableduring starting of the gas turbine engine, a mechanical locking deviceis provided to hold the spline actuating piston 64, in the positionshown in FIG. 4, to retain the spline shaft 24 out of driven engagementwith the drive shaft 18.

Such a mechanical locking device is shown in FIG. 3 and includes acup-shaped plunger housing 153 which may be formed as part of the gearcasing 11 or as a separate element suitably secured thereto. The plungerhousing 153 is closed at one end by cap 154 and slideably carries withina stepped bore 155 therein a plunger 156 carrying an upstanding lock pin157. As seen in FIG. 3, plunger 156 is normally biased upward by aspring 158 whereby lock pin 157 is engageable in a lock slot 6412provided in the spline actuator piston 64. The chamber above the plunger156 is in communication via a port 161 and conduit 162 to the dischargeside of pump 86 whereby as the pump 86 operates to supply pressurizedhydraulic fluid to the remaining control elements of the propellercoupling, the plunger 156 is moved downward against the biasing actionof spring 158 to disengage the lock pin from the lock slot 64b to freethe supply actuator piston 64. The stepped bore 155 is also connectedvia port 163 and a return conduit 164 to the sump 87 for return ofhydraulic fluid passing around the periphery of the plunger 156 into thechamber below this plunger.

The above-described propeller coupling arrangement is for use in anaircraft employing a gas turbine engine to drive a main helicopter rotorand tail rotor, both not shown, plus, and at predetermined forward speedconditions, to drive a propeller to efiect increased forward speed ofthe aircraft.

The propeller 13 is provided with a conventional variable pitch controlmechanism, not shown, whereby the propeller blade angle can be varied,as required, including a blade angle position in which the propeller isfeathered. In addition, rotation of the propeller shaft 35 can becontrolled by a conventional propeller shaft brake, not shown, since thedetails of its structure are not pertinent to the subject invention.

The control requirements for operation of the aircraft using thepropeller coupling of the invention are as follows:

I. The propeller shaft 35 is braked, with the blade angle of thepropeller 13 in feathered position, and the propeller shaft,

through the propeller coupling of the invention, is disengaged duringall helicopter type operations.

2. When the pilot desires to use the propeller for forward propulsion,he manually controls disengagement of the propeller brake and manuallycontrols the blade angle of the propeller to allow the propeller towindmill and, in addition, he selects propeller shaft engagementmanually as by energizing the solenoid valve 91 through a suitableswitch and power circuit, not shown.

3. Hydraulic fluid acting on the clutch actuating piston 63 and splineactuating piston 64 will engage first the disc clutch and then thesynchronous clutch and, when the propeller shaft and power turbine shaftspeeds are synchronized, considering the gear ratios between theseelements, the sliding spline shaft 24 is engaged with the drive shaft 18to drive the propeller shaft. The disc clutch is then released.

4. When it is desired to return to a helicopter only mode of operation,the pilot manually selects propeller shaft disengagement, as byde-energizing the solenoid valve 91.

5. The disc clutch, as described above, is again applied during splineshaft 24 disengagement with the drive shaft 18 and, followingdisengagement, the disc clutch is again released.

6. The pilot then manually feathers the propeller blade and thepropeller brake is again applied to retain the propeller shaft againstrotation.

A clear understanding of the operation of the propeller coupling canbest be obtained by reference to the schematic hydraulic fluid circuitof FIG. 4 and the following description.

The operation of the propeller coupling utilizes only signals generatedin the transmission assembly plus the pilot operated switch, such as theswitch used to energize the solenoid valve 91. In addition, a Pitotpressure is generated in a conventional manner, not shown, such that dueto centrifugal force, the Pitot pressure thus generated is proportionalto the propeller shaft speed squared. The hydraulic control system, aspreviously described, consists of three basic valves which determine theporting of high and low pressure hydraulic fluid to the two actuatingpistons of the system, that is, to the clutch actuating piston 63 and tothe spline actuator piston 64. These valves are the shuttle valve 93which essentially compares the requested position of the spline actuatorpiston with its actual position, the pilot operated solenoid valve 91which in essence provides the spline actuator piston requested signaland, the Pitot pressure actuated valve 92 in which the Pitot pressure, arough measure of propeller shaft speed, is balanced against the force ofspring 110. Valve 92 operates essentially as a shuttle valve andrequires a spring 110 with high preload but low spring rate.

Referring now to the operation of the propeller coupling of theinvention, FIG. 4 illustrates the normal condition of the variouscomponents when the propeller coupling is in a disengaged, nondrivingcondition. In this condition, the friction clutch plates 45 and 51 ofthe disc clutch are not in driving engagement with respect to eachother, and the spline shaft 24 is not engaged with the drive shaft 18,the spline actuating piston 64 being in the position shown and retainedat this position by the lock mechanism of FIG. 3.

After engine start, the valves are as shown in FIG. 4 with the solenoidvalve 91, not energized so that as the pump 86 operates, high pressurehydraulic fluid is conveyed via con-- duits 131, 135 through theuncovered ports 97 and 98 and valve 91 to the conduit 151 to apply highpressure to one end of the spool valve 112 in shuttle valve 93. Thishigh pressure hydraulic fluid is also conveyed through orifice 149 andconduit 148 and passage 84 into the cavity 66 to force the splineactuator piston 64 toward the right, to retain it in the position shownin FIG. 4. Of course, as this pressure builds up in cavity 66, it willalso build up in the chamber above plunger 156 to move it and thereforelock pin 157 out of locking engagement with the spline actuator piston.With the spline actuator piston 64 in this position, the vent passage 85is blocked thereby blocking the vent path from the opposite end of theshuttle valve 93, right-hand end as seen in this figure, thereby causinghigh pressure hydraulic fluid to be maintained in the righthand end ofthis valve resulting in a balanced spool valve position in the shuttlevalve, allowing venting of the clutch actuating piston cavity 65.

When the pilot actuates the solenoid valve 91, the valve spool is movedto the right, with respect to FIG. 4, to uncover port 96 while coveringport 97 in this valve. At this time, the pilot also manually unfeathersthe propeller and regulates the blade angle of the propeller to allowthe propeller to begin windmilling toward synchronous speed with respectto the output shaft of the gas turbine engine 10, considering, ofcourse, the gear ratios between these two elements. However, when thepropeller speed, as indicated by the Pitot pressure, is well below thesynchronous level, this Pitot pressure is insufficient to overcome thebiasing action of the spring in valve 92 so that the spool valve 102 ofthis valve remains in the position as shown in FIG. 4 and thus thepressures to the shuttle valve 93 remain unchanged and the pressures inthe cavities 65 and 66 remain unchanged from that described in theproceeding paragraph.

When the propeller shaft is windmilling at a speed approximatelyproportional to the engine speed, the Pitotpressure will be sufficientto move the spool valve 102 to the right, in terms of FIG. 4, to thenplace port 107 in communication with port 109 of this valve to permitcontrolled venting of hydraulic fluid from the cavity 66 through theorifice 149 and permit venting of the left end of the shuttle valve 93.Since the motion of the spline actuator piston 64 is restricted byfrictional engagement with the cylinder 61, the vent passage 85 remainsblocked for a period of time so that high pressure hydraulic fluid isstill applied to the right end of the spool 112 of the shuttle valve 93to shift it to the left, in terms of FIG. 4, whereby theland e uncoversthe passage 115 to allow high pressure hydraulic fluid from conduit 137to flow through port 1 l3, conduit 147 and 146 and passage 83 into thecavity 65 to force the clutch actuating piston 63 to the left causingthe disc clutch to be applied. This delay in applying the disc clutchuntil the two speeds, that of the propeller shaft and that of the engineoutput shaft, in this case, drive shaft 18, are within a given range isemployed to minimize disc clutch wear.

With the cavity 66 now being vented to effect a reduction of hydraulicpressure therein, the force of spring 71 will now be suflicient to forcethe spline actuator piston 64 to the left to the position shown in FIG.2 and, at the same time, the friction driven ring 78 is also moved tothe left and is further biased by spring 79 into driven frictionalengagement with the friction drive ring 47. Relative rotation betweenthe friction drive ring 47 and the friction driven ring 78, indicatingnonsynchronous speeds, produces a reaction force through the helicalspline engagement between the friction driven ring 78 and the splineshaft 24 such that when the propeller shaft speed is below turbinespeed, that is, the speed of drive shaft 18 is driven by the turbineengine, additional spline actuator piston 64 and spline shaft 24 motionto the left in terms of FIG. 4 is prevented. When these shaft speeds aresynchronized, this reaction force disappears and the spline actuatorpiston with the friction ring 78 and the spline shaft 24 move toward theleft, to the position shown in FIG. 2, causing the spline shaft 24 to bein driven engagement with drive shaft 18.

When the spline actuating piston moves toward the left, toward theposition shown in FIG. 2, the vent passage 85 is uncovered allowing theright end of the shuttle valve, as seen in FIG. 4, to be vented throughthe conduits 133 and and vent passage 85, this occurs since the flow ofhydraulic fluid from the pump 86 to this end of the shuttle valve islimited by the orifice 132. The spool valve 112 of shuttle valve 93 thenreturns toward the neutral position with the land e thereon blocking theport 115 to now permit venting of the cavity 65 to release the clutchactuating piston 63 to effect disengagement of the disc clutch.

When the pilot wishes to disengage the propeller, he deenergizes thesolenoid valve 91 allowing the spring 99 to force the spool valve 95back to the position shown in FIG. 4 to uncover the high pressure port97 and allow hydraulic fluid to flow to the left-hand end of the shuttlevalve 93, forcing the spool valve 112 to the right placing the port 115in communication with the port 118 whereby high pressure hydraulic fluidid again supplied to the piston cavity 65 to re-engage the disc clutch,as previously described. At the same time, high pressure fluid willgradually flow through the orifice 149 to effect movement of the splineactuator piston 64 to the right, effecting disengagement of the splineshaft 24 from the drive shaft 18. The orifice 149 is used to delay theflow of high pressure fluid to the piston cavity 66 so that the discclutch can be applied before the synchronous clutch is disengaged tominimize side load on the drive spline teeth 22 and 23 during theirdisengagement.

As the spline actuator piston 64 again moves to the right, to theposition shown in FIG. 4, vent passage 85 is again blocked, allowingpressure on opposite sides of the spool valve 112 of valve 93 to becomeequalized thus shifting the spool valve back to the position shown inthis figure wherein the land e thereon blocks the port 115. This allowsthe clutch piston cavity 65 to be vented, to again release the discclutch. At the same time, the pilot feathers the propeller causing it tolose rotationalspeed and the the pilot engages the propeller shaft brakewhereby the Pitot pressure is reduced allowing the spool valve 102 toagain return to the position shown in FIG. 4 by the biasing action ofspring 1 10 at which time the conditions shown in this figure are againattained.

What is claimed is:

l. A propeller coupling to selectively couple a gas turbine engine to apropeller shaft including a splined input shaft driven by the gasturbine engine, an output shaft operatively connected to the propellershaft, a splined intermediate shaft operatively connected for rotationwith said output shaft and slideably positioned with respect to saidsplined input shaft for movement between a first position out of splinedengagement to a second position in splined engagement with respect tosaid splined input shaft, a clutch means selectively operable todirectly connect said splined input shaft in driving engagement throughsaid clutch means with said splined intermediate shaft and clutch andactuator means operatively connectable to said splined intermediateshaft to effect movement of said splined intermediate shaft between saidfirst position and said second position and driven by said splined inputshaft to synchronize the rotational speed of said splined intermediateshaft to the speed of the splined input shaft before completing themovement of the splined intermediate shaft to said second position toeffect the splined positive drive engagement between said shafts.

2. A propeller coupling according to claim 1 wherein said clutch meansincludes a disc clutch having torque input means connected to saidsplined input shaft and torque output means connected to said splinedintermediate shaft, a fluid pressure operated actuator for said discclutch to effect a clamp-up force between said torque input means andsaid torque output means, and wherein said clutch and actuator meansincludes a synchronous clutch having a torque input means connected tosaid splined input shaft and a torque output means slideably connectedto said splined intermediate shaft and, an actuator member for movingsaid splined intermediate shaft between said first position and saidsecond position and to bias said torque output means of said synchronousclutch into driven engagement with said torque input means of saidsynchronous clutch.

3. A propeller coupling to selectively couple a propeller shaft to anengine, said coupling including, a driven shaft operatively connected tothe propeller shaft, a drive shaft operatively connected to the engine,said drive shaft having drive splines thereon, a spline shaft havingdriven splines thereon operatively connected to said driven shaft forrotation therewith and slideable axially with respect therefor formovement from a first position with said driven splines thereon out ofengagement with said drive splines on said drive shaft to a secondposition with said driven splines in en agement with said drive splines,a disc clutch means selective y operable to connect said drive shaft indriving engagement with said spline shaft, and, spline actuator meansincluding a synchronous clutch means operatively connected to saidspline shaft for moving said spline shaft between said first positionand said second position, said synchronous clutch means beingoperatively connectable to said drive shaft and operable to preventmovement of said spline shaft to said second position until therotational speed of said spline shaft is synchronized with therotational speed of said drive shaft.

4. A propeller coupling according to claim 3 wherein said disc clutchmeans includes a clutch drive ring fixed for rotation with said driveshaft, a clutch driven ring fixed for rotation with said drive shaft, aclutch driven ring fixed for rotation with said spline shaft, aplurality of adjacent friction plates alternately connected to saidclutch drive ring and said clutch driven ring for rotation therewith,and means including a fluid pressure operated clutch actuating pistonabuttable with respect to said friction plates for exerting a clamp-upforce thereon.

5. A propeller coupling according to claim 3 wherein said splineactuator means includes a spline actuating piston means connected tosaid spline shaft for effecting sliding movement of said spline shaftbetween said first position and said second position, said splineactuating piston means including spring means to normally bias saidspline shaft toward said second position, and wherein said synchronousclutch means includes a spring biased cone clutch driven member having ahelical spline engagement with said spline shaft and a complementarycone clutch drive member fixed for rotation with said drive shaft.

UNITED STATES PATENT OFFICE 5 9 CERTIFICATE OF CORRECTIN Patent No.306790033 Dated y 72 Inventor) Douglas A. Wagner It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected asshown below:

Patent Column 2, line 47, after "means", delete in the form of PatentColumn 7, line 5, "id" should read is i and,

Patent Column 8, line 34, after "shaft", delete a clutch driven ringfixed for rotation with said dri shaft,.

Signed and sealedthis 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner-0f Patents

1. A propeller coupling to selectively couple a gas turbine engine to apropeller shaft including a splined input shaft driven by the gasturbine engine, an output shaft operatively connected to the propellershaft, a splined intermediate shaft operatively connected for rotationwith said output shaft and slideably positioned with respect to saidsplined input shaft for movement between a first position out of splinedengagement to a second position in splined engagement with respect tosaid splined input shaft, a clutch means selectively operable todirectly connect said splined input shaft in driving engagement throughsaid clutch means with said splined intermediate shaft and clutch andactuator means operatively connectable to said splined intermediateshaft to effect movement of said splined intermediate shaft between saidfirst position and said second position and driven by said splined inputshaft to synchronize the rotational speed of said splined intermediateshaft to the speed of the splined input shaft before completing themovement of the splined intermediate shaft to said second position toeffect the splined positive drive engagement between said shafts.
 2. Apropeller coupling according to claim 1 wherein said clutch meansincludes a disc clutch having torque input means connected to saidsplined input shaft and torque output means connected to said splinedintermediate shaft, a fluid pressure operated actuator for said discclutch to effect a clamp-up force between said torque input means andsaid torque output means, and wherein said clutch and actuator meansincludes a synchronous clutch having a torque input means connected tosaid splined input shaft and a torque output means slideably connectedto said splined intermediate shaft and, an actuator member for movingsaid splined intermediate shaft between said first position and saidsecond position and to bias said torque output means of said synchronousclutch into driven engagement with said torque input means of saidsynchronous clutch.
 3. A propeller coupling to selectively couple apropeller shaft to an engine, said coupling including, a driven shaftoperatively connected to the propeller shaft, a drive shaft operativelyconnected to the engine, said drive shaft having drive splines thereon,a spline shaft having driven splines thereon operatively connected tosaid driven shaft for rotation therewith and slideable axially withrespect therefor for movement from a first position with said drivensplines thereon out of engagement with said drive splines on said driveshaft to a second position with said driven splines in engagement withsaid drive splines, a disc clutch means selectively operable to connectsaid drive shaft in driving engagement with said spline shaft, and,spline actuator means including a synchronous clutch means operativelyconnected to said spline shaft for moving said spline shaft between saidfirst position and said second position, said synchronous clutch meansbeing operatively connectable to said drive shaft and operable toprevent movement of said spline shaft to said second position until therotational speed of said spline shaft is synchronized with therotational speed of said drive shaft.
 4. A propeller coupling accordingto claim 3 wherein said disc clutch means includes a clutch drive ringfixed for rotation with said drive shaft, a clutch driven ring fixed forrotation with said drive shaft, a clutch driven ring fixed for rotationwith said spline shaft, a pluralitY of adjacent friction platesalternately connected to said clutch drive ring and said clutch drivenring for rotation therewith, and means including a fluid pressureoperated clutch actuating piston abuttable with respect to said frictionplates for exerting a clamp-up force thereon.
 5. A propeller couplingaccording to claim 3 wherein said spline actuator means includes aspline actuating piston means connected to said spline shaft foreffecting sliding movement of said spline shaft between said firstposition and said second position, said spline actuating piston meansincluding spring means to normally bias said spline shaft toward saidsecond position, and wherein said synchronous clutch means includes aspring biased cone clutch driven member having a helical splineengagement with said spline shaft and a complementary cone clutch drivemember fixed for rotation with said drive shaft.